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package javax.naming.spi;

import java.util.Hashtable;
import javax.naming.*;
import javax.naming.directory.Attributes;

/**
 * This interface represents a factory for creating an object given
 * an object and attributes about the object.
 * <p>
 * The JNDI framework allows for object implementations to
 * be loaded in dynamically via <em>object factories</em>. See
 * <tt>ObjectFactory</tt> for details.
 * <p>
 * A <tt>DirObjectFactory</tt> extends <tt>ObjectFactory</tt> by allowing
 * an <tt>Attributes</tt> instance
 * to be supplied to the <tt>getObjectInstance()</tt> method.
 * <tt>DirObjectFactory</tt> implementations are intended to be used by <tt>DirContext</tt>
 * service providers. The service provider, in addition reading an
 * object from the directory, might already have attributes that
 * are useful for the object factory to check to see whether the
 * factory is supposed to process the object. For instance, an LDAP-style
 * service provider might have read the "objectclass" of the object.
 * A CORBA object factory might be interested only in LDAP entries
 * with "objectclass=corbaObject". By using the attributes supplied by
 * the LDAP service provider, the CORBA object factory can quickly
 * eliminate objects that it need not worry about, and non-CORBA object
 * factories can quickly eliminate CORBA-related LDAP entries.
 *
 * @author Rosanna Lee
 * @author Scott Seligman
 * @see NamingManager#getObjectInstance
 * @see DirectoryManager#getObjectInstance
 * @see ObjectFactory
 * @since 1.3
 */

public interface DirObjectFactory extends ObjectFactory {

  /**
   * Creates an object using the location or reference information, and attributes
   * specified.
   * <p>
   * Special requirements of this object are supplied
   * using <code>environment</code>.
   * An example of such an environment property is user identity
   * information.
   * <p>
   * <tt>DirectoryManager.getObjectInstance()</tt>
   * successively loads in object factories. If it encounters a <tt>DirObjectFactory</tt>,
   * it will invoke <tt>DirObjectFactory.getObjectInstance()</tt>;
   * otherwise, it invokes
   * <tt>ObjectFactory.getObjectInstance()</tt>. It does this until a factory
   * produces a non-null answer.
   * <p> When an exception
   * is thrown by an object factory, the exception is passed on to the caller
   * of <tt>DirectoryManager.getObjectInstance()</tt>. The search for other factories
   * that may produce a non-null answer is halted.
   * An object factory should only throw an exception if it is sure that
   * it is the only intended factory and that no other object factories
   * should be tried.
   * If this factory cannot create an object using the arguments supplied,
   * it should return null.
   * <p>Since <tt>DirObjectFactory</tt> extends <tt>ObjectFactory</tt>, it
   * effectively
   * has two <tt>getObjectInstance()</tt> methods, where one differs from the other by
   * the attributes argument. Given a factory that implements <tt>DirObjectFactory</tt>,
   * <tt>DirectoryManager.getObjectInstance()</tt> will only
   * use the method that accepts the attributes argument, while
   * <tt>NamingManager.getObjectInstance()</tt> will only use the one that does not accept
   * the attributes argument.
   * <p>
   * See <tt>ObjectFactory</tt> for a description URL context factories and other
   * properties of object factories that apply equally to <tt>DirObjectFactory</tt>.
   * <p>
   * The <tt>name</tt>, <tt>attrs</tt>, and <tt>environment</tt> parameters
   * are owned by the caller.
   * The implementation will not modify these objects or keep references
   * to them, although it may keep references to clones or copies.
   *
   * @param obj The possibly null object containing location or reference information that can be
   * used in creating an object.
   * @param name The name of this object relative to <code>nameCtx</code>, or null if no name is
   * specified.
   * @param nameCtx The context relative to which the <code>name</code> parameter is specified, or
   * null if <code>name</code> is relative to the default initial context.
   * @param environment The possibly null environment that is used in creating the object.
   * @param attrs The possibly null attributes containing some of <tt>obj</tt>'s attributes.
   * <tt>attrs</tt> might not necessarily have all of <tt>obj</tt>'s attributes. If the object
   * factory requires more attributes, it needs to get it, either using <tt>obj</tt>, or
   * <tt>name</tt> and <tt>nameCtx</tt>. The factory must not modify attrs.
   * @return The object created; null if an object cannot be created.
   * @throws Exception If this object factory encountered an exception while attempting to create an
   * object, and no other object factories are to be tried.
   * @see DirectoryManager#getObjectInstance
   * @see NamingManager#getURLContext
   */
  public Object getObjectInstance(Object obj, Name name, Context nameCtx,
      Hashtable<?, ?> environment,
      Attributes attrs)
      throws Exception;
}
